Nikon 1.8g's vs Sigma 1.4 Art Series

I ended up purchasing the Sigma 35mm and 50mm 1.4 Art lenses when I got my D800e. Image quality wise I can't complain at all but I am really tempted to sell them and go for a couple of Nikon 1.8g lenses instead (the 28mm 1.8g and 50mm 1.8g seem the best bet but the 50mm 1.4g does have a wider throw on the focus ring which is handy for video).

Why? The Sigma lenses are heavy and huge! I already have my heavy zooms so when I put primes on I feel like the camera should weigh significantly less. The size and weight difference between the 50mm lenses is absolutely huge.

I should note: I've since started filming on the A7S and the weight definitely is much more of a factor on that small camera which is adding to my temptation.

From what I can see the Nikon 1.8g lenses ain't bad, particularly the 28mm. It just seems like these days no one bothers with these primes and goes for the Sigma so I wouldn't mind some opinions